Current processes for amination of alcohols and/or diols typically employ heterogeneous catalysts which comprise supported transition metals with known hydrogenation/dehydrogenaton activity and/or acidic compositions such as zeolites, mixed oxides, and metal phosphates. Catalysts containing transition metals typically yield by-product amines and olefinic amines which deactivate the catalyst and often produce undesirable aldehyde-type by-products. Acidic catalysts are usually non-selective for alcohol amination reactions and yield the corresponding ether, unsaturated hydrocarbon, polymeric product and scrambled amines as by-products via transalkylation and disproportionation reactions.
Synthetic methods heretofore utilized for production of aliphatic and aromatic amines include amination of alcohols with ammonia/amines in the presence of hydrogenation/dehydrogenation catalysts, amination of alcohols with ammonia/amines using acidic dehydration-type catalysts and reductive amination of aldehydes and ketones over transition metal catalysts.
However, such catalysts tend to dehydrate alcohols to form olefin or ether by-products thereby reducing the yield of the desired amination product. To avoid high alkene formation which promotes catalyst deactivation, acidic catalysts are typically operated at lower temperatures. Unfortunately, lower reaction temperatures reduce reaction efficiency because lower amine/alcohol ratios are required to achieve high amine conversion. Additionally, both acidic and dehydrogenation-type catalysts inherently require some recycle of unconverted reactants.
Several acid metal phosphate catalysts, particularly phosphates of boron, aluminum and trivalent iron, have been proposed for use in intramolecular cyclic dehydration reactions and other condensation reactions involving amine compounds. Examples of such reactions are found in U.S. Pat. No. 4,117,227, which discloses conversion of an N-substituted diethanolamine to the corresponding N-substituted morpholine. Additionally. U.S. Pat. No. 4.049,657 discloses reaction of piperidine with ethanolamine over metal phosphate catalysts to produce N-aminoethyl piperidine.
U.S. Pat. No. 4,082,805 relates to a process for the production of aliphatic amines by reacting a C.sub.1 to C.sub.5 alcohol or ether with ammonia in the presence of a crystalline aluminosilicate catalyst having the structure of ZSM-5, ZSM-11 or ZSM-21. Preferred catalysts have a high silica to alumina ratio, typically greater than 5 and preferably greater than 30. The reaction is effected at a temperature between 300.degree. C. and about 500.degree. C. a pressure between atmospheric and 1000 psig with the relative feed rates, expressed in grams per hour of alcohol or ether to ammonia within the approximate range of 1:1 to about 5:1.
U.S. Pat. 4,501,889, assigned to Air Products and Chemicals, Inc. discloses a process for preparing morpholine compounds by reacting 2-(2-aminoethoxy)ethanol in the presence of a catalyst selected from the group consisting of the pyrophosphate. monohydrogen phosphate and dihydrogen phosphate of strontium, copper, magnesium, calcium, barium, zinc, aluminum, lanthanum, cobalt, nickel, cerium and neodymium and mixtures thereof Preferred catalysts are the soluble metal salts of strong acids such as metal nitrates in substantially stoichiometric proportion to the phosphate.